Electrolysis

Question 1

what is electrolysis?

Answer 1

a process that uses an electric current to split up a substance that contains ions

Question 2

what type of substance is electrolysis often used to break down?

Answer 2

ionic compounds.

Question 3

what had to be done to a solid ionic compound before it can be put through electrolysis?

Answer 3

an ionic compound has to be in a molten or aqueous form to be electrolysised because as a solid, ionic compounds don’t conduct electricity.

Question 4

what is the name of a substance broken down by electrolysis?

Answer 4

an electrolyte

e.g lead bromide

Question 5

what is the positive electrode called?

Answer 5

anode

Question 6

what is the negative electrode called?

Answer 6

cathode

Question 7

what is the equasions for e.g cl^(-)

Answer 7

2cl^(-) > cl(2) + 2e

Question 8

what is the equasion for e.g cu^(2+)?

Answer 8

cu^(2+) + 2e^(-) > cu

Question 9

what is an anion?

Answer 9

a negative ion

Question 10

what is a cation?

Answer 10

positive ion

Question 11

what is oxidation?

Answer 11

the loss of electrons

Question 12

what is reduction?

Answer 12

the gain of electrons

Question 13

what is often used for electrodes and why?

Answer 13

graphite

• it’s unreactive
• it conducts electricity

Question 14

if molten magnesium oxide is electrolysed

which ions go to the positive electrode and why?

Answer 14

• the negative ions because opposites attract

- (oxygen)

Question 15

is e.g 2O^(2+) > O^(2) + 4e^(-)

oxidation or reduction?

Answer 15

oxidation- the loss of electrons

Question 16

when molten magnesium oxide is electrolysed what forms at the cathode?

Answer 16

magnesium

Question 17

what is a halogen?

Answer 17

a group 7 element

Question 18

why is the rule for predicting the product at the positive electrode?

Answer 18

if the -ve ions are halogens then they are formed, otherwise oxygen will be formed.

Question 19

what is the rule for predicting the product at the negative electrode?

Answer 19

if the +ve ions are less reactive than hydrogen then they are formed, otherwise hydrogen is formed.

Question 20

what is a use of hydrogen?

Answer 20

used in the manufacture of margarine

Question 21

describe the test for hydrogen gas?

Answer 21

when hydrogen is present a squeaky pop will be heard in the presence of a little spling

Question 22

describe the test for chlorine gas

Answer 22

it makes damp litmus paper turn red and then bleaches it white

Question 23

what does purple UI indicate?

Answer 23

alkaline solution (ph 8-14)

Question 24

what does green UI indicate?

Answer 24

neutral solution (ph 7)

Question 25

what does red UI indicate?

Answer 25

acidic solution (6-1)

Question 26

what is electroplating?

Answer 26

when an object has been coated with a thin layer of metal by electrolysis

Question 27

give 2 reasons why something might be electroplated

Answer 27

- to make it less corrosive | - harder

Question 28

why does graphite conducts electricity?

Answer 28

each carbon atom only has 3 bonds to other carbon atoms, leaving 1 delocalised electron per carbon atoms.

Question 29

define electrolyte

Answer 29

the substance broken down by electrolysis

Question 30

define electrode

Answer 30

the material that carries an electrical current

Question 31

name 3 products formed form the electrolysis of brine

Answer 31

- chlorine - bleach - hydrogen